Bridge plugs have long been used in the oil and gas industry to control the flow of fluid through the well. A bridge plug commonly may employ resilient elastomeric sealing rings and anchoring slips, and may either seal off all flow through the well to isolate a lower interval from an upper interval in a well, or may be supplied with an internal passage or a choke to reduce or control flow through tubular at a desired depth.
A compression set bridge plug adaptable for through tubing operations is disclosed in U.S. Pat. No. 5,678,635. The anchor mechanism includes upper and lower independently movable slips. U.S. Pat. No. 4,436,150 discloses a bridge plug with an internal bypass passage which is closed when the bridge plug is set. The bridge plug includes external slips on a slip carrier. Bridge plugs are commonly hydraulicly or mechanically set. While various procedures have been employed for setting the bridge plug, sealing reliability between the bridge plug and the wall of the tubular in the well has been a significant problem, particularly when intended to seal off high pressure gas below the bridge plug.
The problems with the existing bridge plugs include poor reliability, particularly to seal gas in a well after the bridge plug has been set. In a subsea well, for example, tubular may be cut at or below the mud line and a bridge plug placed in the well to completely seal off the well. If gas bypasses the bridge plug, it bubbles to the surface and creates environmental hazzards. Accordingly, expensive remedial action must be taken to set another bridge plug in the well to stop the inadvertent flow of gas from the well.
The disadvantages of the prior art are overcome by the present invention, and an improved bridge plug assembly and method of setting a bridge plug in a well are hereinafter disclosed.